Ask Hannibal King, once a vampire always a vampire. He was supposed to have been cured when Dr Strange cast the Montesi Formula, but he was reverted for the Midnight Sons junk of the 90's.

Though making her a vampire was pretty stupid.

Hannibal King _is_ a vampire/supernatural character, so of course the vampirism will easily stick to him and be hard to get rid of. It naturally belongs to stories he will feature in.

I would be very surprised to hear about Jubilee becoming a vampire again in the future. Someone could possibly do some one-off stories with her featuring vampires, but anything more than that seems unlikely.